Microsoft Visual C++ 6 is COM enabled. In dialog based MFC applications, you can use Dynamic TWAIN "visually" in the IDE. In non-dialog based MFC applications, such as MDI or SDI applications, you need to write code to add the Dynamic TWAIN to your applications.
The topics about how to use Dynamic TWAIN in these two different kinds of application are:
Using Dynamic TWAIN in Microsoft Visual C++ Dialog Based Applications
Using Dynamic TWAIN in Microsoft Visual C++ Non-Dialog Based Applications